It might be a problem with the game.The game automatically changes the video resolution when it starts.

"FH4 KNOWN ISSUES [UPDATED: OCTOBER 1ST, 2018: 5:33 PM PT" by FORZA TOTAL."Running with an Overlay or On Screen Display via MSI Afterburner, RivaTuner or EVGA Precision XOC can cause the game to crash at launch or during gameplay. "